The capacity of gas centrifuges to enrich uranium increased by two orders of magnitude between 1961 and 1967, from 0.39 kg-SWU/year to 30 kg-SWU/year. That striking fact was declassified by the U.S. Department of Energy in 2008 and made public this month.

Under the terms of the Atomic Energy Act (section 142), which governs the classification of nuclear weapons-related information, the Department of Energy is required to conduct a "continuous review" of its classified information "in order to determine which information may be declassified." And so it does.

Slowly and methodically, the Department has declassified numerous categories of nuclear information over the last several years. Those declassification actions were documented recently in response to a Freedom of Information Act request from the Federation of American Scientists.

In each instance, declassification is preceded by a deliberative process which considers whether the information is already widely known; whether its publication would assist an adversary in the development of countermeasures to U.S. systems or in development of its own nuclear capability; whether disclosure would have a detrimental effect on U.S. foreign relations; whether it would benefit the public welfare; and whether it would otherwise enhance government operations.

With respect to the declassification of historical U.S. centrifuge information, the DOE record of decision noted that while the information was not widely known, it would not assist in development of countermeasures, would not have a detrimental effect on foreign relations, and would not enhance government operations. Other aspects of the justification for declassification of centrifuge data, however, remained classified and were not released.

On the whole, DOE seems to have a well-articulated procedure for conducting declassification of atomic energy information. Under DOE regulations, there is even a provision for members of the public to propose topics for declassification (10 CFR 1045.20), though it has rarely if ever been invoked.

The outcome of the declassification process, however, is somewhat unpredictable. It is contingent upon an official -- but inevitably subjective -- assessment of current technological developments and political trends. The correct answer is not always self-evident.

"Prior classification decisions, while not unwarranted, might have taken a slightly different direction had the post-Cold War environment been more clearly seen a decade ago," wrote a Los Alamos technical evaluation panel in a 2003 report to DOE headquarters.

Classified atomic energy information still plays a potent role in public policy and is not exclusively the province of technologists. This week the Nuclear Regulatory Commission granted a license to General Electric-Hitachi for construction of a uranium enrichment plant in Wilmington, NC, which uses a controversial laser enrichment process known as SILEX. Arms control advocates (including FAS) and others argued that the SILEX process raises distinctive proliferation concerns that weigh against its adoption.

Aside from nuclear weapons information classified under the Atomic Energy Act, the Department of Energy also classifies national security information by executive order. DOE described the current state of its national security information program in a recent report on its performance of the Fundamental Classification Guidance Review.

One of the features that make Congressional Research Service reports broadly valuable is that they often reflect the privileged access to executive branch information that is enjoyed by CRS, at least in some areas, compared to what an ordinary member of the public can expect. So, for example, a newly updated CRS report on Central Asia provides authoritative tabulations of US foreign assistance to Central Asian countries, broken down by country and by year for the past two decades. Assembling this data independently would be a difficult and time-consuming chore, if it were possible at all. See Central Asia: Regional Developments and Implications for U.S. Interests, updated September 19, 2012: